Should I Treat The Asymptomatic Siblings Of The Patient Who Has A Positive Rapid Streptococcal Antigen Test?

In general, when deciding to use antimicrobial therapy, the clinician should consider 2 principles:

1. A desire to limit the potential adverse effects to the individual that may be associated with use of the antimicrobial.

2. A desire to limit the potential adverse effects to the larger population that may result from increasing antimicrobial resistance related to exposure to unnecessary antibiotics.

These principles are considered in the context of a desire to limit the duration and severity of acute illness, to decrease the likelihood of complications of infection, and to reduce ongoing transmission and spread of disease.

With these principles and goals in mind, the clinician’s focus should be on maximizing the number of cases of group A streptococcal (GAS) pharyngitis identified and appropriately treated while also minimizing the number of individuals tested and treated who do not have infection. These principles are especially true when considering asymptomatic siblings or other asymptomatic household contacts. Kikuta et al evaluated the role of chemoprophylaxis for siblings of patients with GAS pharyngitis.1 Siblings receiving antibiotic prophylaxis with either penicillin or a cephalosporin for 3 to 5 days were compared with those receiving no prophylaxis. Within the subsequent 30 days, GAS pharyngitis was diagnosed in 3.0% of the prophylaxis group and in 5.3% of the control (nonprophylaxis) group, a difference that was statistically significant. However, the positive impact of prophylaxis was seen only with cephalosporins (not penicillin) and only if the prophylaxis was continued for 5 days. These authors did not recommend routine prophylaxis given the low rate of infection in sibling contacts, the generally benign course of GAS pharyngitis, and the cost of prophylaxis, both monetarily and in terms of potential adverse drug events and the selection of resistant flora. Consequently, asymptomatic individuals should generally not be tested or treated, including siblings of those who test positive for GAS.2,3 It is well known that a significant percentage (10% to 20%) of asymptomatic school-aged children are colonized with GAS, with this number likely toward the upper end of the range when GAS is widespread in the community.4

Additionally, it is well known that ~25% of household contacts of a patient with GAS pharyngitis will become colonized after exposure. However, only a portion of these individuals will develop disease, with the ultimate risk of disease in contacts being in the range of 5% to 10%. Therefore, testing will fairly often result in positive findings, but this will most often reflect colonization rather than disease. Testing and treating positive findings will then result in a significant amount of inappropriate treatment, or at the very least, these findings will require an extensive and sometimes difficult explanation of carrier status to patients and parents.

Although contacts are at increased risk for infection,5 asymptomatic siblings should not be routinely tested or treated unless they are at increased risk for disease complications or unless the positive contact has a known nephritogenic or rheumatogenic strain of the organism.2,3 In this situation, contacts should be tested and then treated if found to be positive. Asymptomatic siblings might also be legitimately tested if the index case has recurrent disease and there is concern that household contacts are involved in the recurrences. In this situation, simultaneous testing and treatment of all positive individuals may have a role in limiting ongoing illness.

Invasive GAS disease is much less common than GAS pharyngitis, occurring in ~3.5/100,000 people in the United States.6 However, the seriousness of an invasive infection leads to questions regarding the role of prophylaxis for household contacts in this situation. In a study coordinated by the Centers for Disease Control and Prevention (CDC), Robinson et al found an attack rate of 66.1/100,000 for confirmed GAS invasive disease among household contacts of index patients with invasive GAS disease.6 Although this study did reveal an apparent increased rate of invasive disease (within 1 month of exposure) in household contacts when compared to the general population, the overall risk of invasive disease remained quite low. The attack rate of 66.1/100,000 was based upon one confirmed case of invasive disease occurring among 1514 household contacts. Even in the context of invasive GAS disease, a working group composed of GAS experts has recommended that no routine prophylaxis be administered to household contacts.7 This recommendation was made because of the low overall risk of invasive disease, the inability to determine those who may be at increased risk, and the lack of a proven prophylactic treatment regimen.

Finally, some families are concerned with the need for testing at the end of a therapeutic course in order to verify bacterial eradication. Such confirmatory testing is not recom- mended. Follow-up testing would be indicated for individuals with signs and symptoms compatible with refractory streptococcal pharyngitis without clinical features consistent with viral illness. Additionally, follow-up testing would be appropriate for individuals at increased risk for acute rheumatic fever or other complications,8 which would include those with history of rheumatic fever, those with history of poststreptococcal glomerulo-nephritis, family members of those with history of these GAS sequelae, individuals with recent varicella infection, and those who are immunosuppressed.

Conclusion

Although some families may push for therapy for asymptomatic family members when one child is diagnosed with GAS pharyngitis, it is helpful for both the clinician and the family to know that there are very few circumstances in which this approach is indicated and that providing therapy to an asymptomatic child, when not indicated, may do more harm than good.

7. The Prevention of Invasive Group A Streptococcal Infections Workshop Participants. Prevention of invasive group A streptococcal disease among household contacts of case patients and among postpartum and post- surgical patients: recommendations from the Centers for Disease Control and Prevention. Clin Infect Dis. 2002; 35(8):950-959.

8. Gerber MA, Baltimore RS, Eaton CB, et al. Prevention of rheumatic fever and diagnosis and treatment of acute streptococcal pharyngitis: a scientific statement from the American Heart Association Rheumatic Fever, Endocarditis, and Kawasaki Disease Committee of the Council on Cardiovascular Disease in the Young, the Interdisciplinary Council on Functional Genomics and Translational Biology, and the Interdisciplinary Council on Quality of Care and Outcomes Research. Circulation. 2009;119(11):1541-1551.